1. Field of the Invention
The present invention relates to an operation microscope apparatus used for an ophthalmologic operation, and more particularly, to an operation microscope apparatus including a front lens for condensing illumination light to illuminate an interior of an eye.
2. Description of the Related Art
Up to now, when a retina and vitreous body operation in an ophthalmologic field is performed, as shown in FIG. 13, an operation contact lens 200 is placed on a cornea Ec of an eye to be operated E. Then, while a light guide (optical fiber) 201 is inserted into an interior of the eye to illuminate an operation region, an operation instrument 202 such as a cutter or a forceps is inserted into the interior of the eye to perform the operation. In FIG. 13, reference symbol Ec denotes the cornea and Ev denotes a vitreous chamber. When the operation is to be performed using the operation method as shown in FIG. 13, it is necessary that an operator hold the light guide 201 in his/her one hand and hold the operation instrument 202 in his/her other hand. This raises a problem in that, for example, it is difficult to perform a fine operation.
In order to deal with the problem, there has been proposed an operation microscope apparatus using a front lens for illuminating the interior of the eye to be operated with illumination light condensed between the eye to be operated and a front focus position of an objective lens (see, for example, JP 2003-062003 A). A plurality of front lenses whose refractive powers are different from one another is prepared. A suitable front lens is selected corresponding to, for example, an observation position of a fundus Er of the eye and attached to the operation microscope apparatus.
FIG. 14 shows an external structure of an operation microscope apparatus 100 using a front lens. The operation microscope apparatus 100 includes a pillar 2 for supporting the operation microscope apparatus 100, a first arm 3 whose one end is connected with an upper end of the pillar 2, a second arm 4 whose one end is connected with the other end of the first arm 3, a drive device 5 connected with the other end of the second arm 4, an operator's microscope 6 suspended from the drive device 5, an assistant's microscope 7 provided adjacent to the operator's microscope 6, and a foot switch 8 for performing various manipulations by a foot. The operator's microscope 6 and the assistant's microscope 7 are three-dimensionally moved in a longitudinal direction and a lateral direction by the drive device 5 in response to manipulation performed by an operator or the like.
The operator's microscope 6 includes a lens barrel section 10 housing, for example, various optical systems and various drive systems. An inverter section 12 housing a known optical unit (image erecting prism) for converting an observation image obtained as an inverted image into an erect image is provided on an upper portion of the lens barrel section 10. A pair of left and right eyepiece sections 11L and 11R are provided on an upper portion of the inverter section 12. The operator looks through the eyepiece sections 11L and 11R to observe the eye to be operated E with both eyes.
The operator's microscope 6 is connected with a front lens 13 through a holding arm 14. The holding arm 14 includes an upper end portion provided to be pivotable in a longitudinal direction, so that the front lens 14 can be removed from a position between the eye to be operated E and a front focus position of an objective lens (not shown). The front lens 13 and the holding arm 14 are stored in a storing section (not shown).
When an eye with the natural lens (phakia) or an eye with the implanted intraocular lens (pseudophakia) is an observation object, relatively weak reflection light on the natural lens or the intraocular lens (IOL) causes a reduction in sharpness of the observation image. Dispersion light from a sclera causes a reduction in contrast of the observation image.
In view of this, it is desirable that the operation microscope apparatus have, for example, (1) a function capable of adjusting a size of an illumination filed and a shape thereof, (2) a function capable of shifting the illumination field, and (3) a function capable of adjusting an angle (illumination angle) between an optical axis (observation optical axis) of an observation optical system and an optical axis (illumination optical axis) of an illumination optical system. In order to realize the functions (1) and (2), there has been known a method of illuminating the interior of the eye with slit light from a slit mechanism incorporated in the illumination optical system (see, for example, JP 2003-062003 A).
FIG. 15 shows a structure of an optical system of the above-mentioned operation microscope apparatus. In the case of the operation microscope apparatus 100 shown in FIG. 14, the optical system is housed in the lens barrel section 10 of the operator's microscope 6 and includes an illumination optical system 20 and a pair of right and left observation optical systems 30. Note that FIG. 15 is a side view showing the optical system as viewed from the assistant's microscope 7 side.
The pair of right and left observation optical systems 30 are provided so as to sandwich an optical axis O of an objective lens 15 on both ends thereof. Each of the right and left observation optical systems 30 includes a zoom lens system 31, a beam splitter 32, an imaging lens 33, an image erecting prism 34, an interpupillary distance adjusting prism 35, a field stop 36, and an eyepiece 37. The zoom lens system 31 is composed of a plurality of zoom lenses 31a, 31b, and 31c. The beam splitter 32 is used to separate a part of observation light exited from the eye to be operated E from the other part thereof to lead the separated part to the assistant's microscope 7 or a TV camera (not shown).
The illumination optical system 20 includes an illumination light source 21, a condenser lens 22, an illumination field stop 23, a slit plate 24, an illumination prism 25, and a collimator lens 27.
The slit plate 24 has a slit hole 24a formed therein. The slit plate 24 can be inserted to and removed from an illumination optical path of the illumination optical system 20. In particular, when the slit plate 24 is to be inserted to the illumination path, the slit plate 24 is moved in a direction orthogonal to an illumination optical axis O′. The slit hole 24a is formed in a direction orthogonal to both the illumination optical axis O′ and a movable direction of the slit plate 24. An image projected onto the fundus of the eye is extended in parallel with a plane including the right and left observation optical axes of the right and left observation optical systems 30.
The illumination field stop 23 is provided in a position optically conjugate with a front focus position F of the objective lens 15. The slit plate 24 is provided near the illumination field stop 23. The slit hole 24a is formed in a position substantially optically conjugate with the front focus position F of the objective lens 15. The objective lens 15 is disposed such that the front focus position F becomes conjugate with the fundus Er (retina) of the eye.
The illumination light source 21 can be housed in the lens barrel section 10 of the operator's microscope 6 or provided outside the lens barrel section 10 to guide the illumination light to the condenser lens 22 of the lens barrel section 10 through an optical fiber.
In order to prevent reflection light of the illumination light on the surface of an operation contact lens or the cornea from entering the observation optical system to cause glare, a structure in which an illumination optical path and an observation optical path are separated from each other on an interface surface on which the reflection light is produced is employed for the conventional operation microscope apparatus.
FIGS. 16A and 16B show suitable separation states in which the illumination optical path and the observation optical path are separated from each other in the cornea Ec of the eye to be operated E. Here, FIG. 16A shows the case where a front lens 13A whose refractive power is 40 diopters (D) is used and FIG. 16B shows the case where a front lens 13B whose refractive power is 80 D is used. FIGS. 17A and 17B show the cases where the separation state shown in FIG. 16A is viewed from above the observation optical system 30. FIGS. 18A and 18B show the cases where the separation state shown in FIG. 16B is viewed from above the observation optical system 30.
The front lens 13A of 40 D as shown in FIG. 16A is used when the fundus Er of the eye and vicinities thereof are observed. Illumination light 301 condensed by the front lens 13A passes through a region 301a on the cornea Ec which is distant from the optical axis O of the objective lens 15 and is incident on the interior of the eye, thereby illuminating the fundus Er of the eye and the vicinities thereof. On the other hand, reflection light (observation light) 401 of the illumination light 301 on the fundus Er of the eye and the vicinities thereof exits from the interior of the eye through a region 401a including the optical axis O of the objective lens 15 and travels to the front lens 13A. Here, it is necessary to provide the region 301a on the cornea Ec through which the illumination light 301 passes and the region 401a through which the observation light 401 passes so as not to overlap with each other, thereby preventing cornea reflection light of the illumination light 301 from mixing with the observation light 401.
At this time, an illumination optical path T and left and right observation optical paths QL and QR in the optical lens 15 become a separation state as shown in FIG. 17A. In the cornea Ec, the region 301a through which the illumination light passes, a region 401aL through which the observation light 401 to be incident on the left observation optical system passes, and a region 401aR through which the observation light 401 to be incident on the right observation optical system passes become a separation state as shown in FIG. 17B.
On the other hand, the front lens 13B of 80 D as shown in FIG. 16B is used when a region distant from the fundus Er of the eye is observed. Even in such a case, it is necessary to provide a region 302a on the cornea Ec through which illumination light 302 passes and a region 402a through which the observation light 402 passes so as not to overlap with each other, thereby preventing cornea reflection light of the illumination light 302 from mixing with the observation light 402.
At this time, the illumination optical path T and left and right observation optical paths QL and QR in the optical lens 15 become a separation state as shown in FIG. 18A. In the cornea Ec, a region 302a through which the illumination light passes, a region 402aL through which the observation light 402 to be incident on the left observation optical system passes, and a region 402aR through which the observation light 402 to be incident on the right observation optical system passes become a separation state as shown in FIG. 18B.
When the operation contact lens is used, although not shown, it is necessary to separate a region on the surface thereof through which the illumination light passes and a region on the surface thereof through which the observation light passes from each other. In addition to this, it is necessary to separate a region on the cornea through which the illumination light passes and a region on the cornea through which the observation light passes from each other.
When the eye to be operated E is significantly displaced in the optical axis O direction of the objective lens 15, the separation state between the illumination light and the observation light is broken. Therefore, it is necessary to ensure the suitable separation states as shown in FIGS. 16A, 16B, 17A, 17B, 18A and 18B in view of the amount of displacement of the eye to be operated E, which moves for the operation.
In the conventional operation microscope apparatus, the separation states are manually ensured by an operation or the like. However, for example, when the operator is not a skilled operator, it is difficult to realize the suitable separation states.
As shown in each of FIGS. 16A and 16B, the suitable separation state between the illumination light and the observation light is changed corresponding to the refractive power of the front lens 13 (13A or 13B). Therefore, every time the front lens 13 is replaced by another one, it is necessary to adjust an illumination angle of the illumination light and a slit width to ensure the suitable separation state, so that the manipulation is troublesome. When the front lens 13 is replaced by another one for the operation, it takes a time to ensure the separation state, with the result that it is likely to unnecessarily prolong the operation.